Evolutionary theory, augmented by a vast literature on gaze cuing and gaze
following, suggests that the unique high-contrast morphology of the human eye
evolved for rapid and silent communication between conspecifics. While this
theory rests on the fundamental idea that humans use their eyes to signal
information, empirical studies have focused exclusively on the effects of
gaze cues on human receivers. In a series of three experiments we examined
the other side of the communication dynamic by investigating if, and when,
humans signal gaze information to other humans in a natural, but controlled,
situation involving food consumption. First, we established that there is a
normative behavior to look away when someone begins to bite. Second, we found
that participants were significantly more likely to look down at their food
before taking a bite when they were eating with another person versus alone.
Lastly, we found that in pairs where a social connection has been
established, when one person looks down signaling that a bite is forthcoming,
the other person tends to look away. These results demonstrate that natural
gaze signaling occurs in the context of eating, and it can, dependent on the
relationship between the pair, trigger a gaze response that is different from
gaze following. Our study shows that natural social attention between
individuals is a two-way street, where each person can signal and read gaze
information, consistent with the idea that human eye morphology evolved to
facilitate communication between conspecifics.